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A  Noiseless  Room  for  Soiind  Experiments 


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[Reprinted  from  Science,  N.  S.,  Vol.  XXVI. ,  No. 
677,  Paget  S73-S8I,  December  SO,  1907] 


A    NOISELESS   ROOM    FOR   SOUND   EXPERIMENTS 

For  many  experiments  in  laboratories  of 
physics,  physiology  and  psychology  a  place  is 
needed  from  which  all,  or  nearly  all,  external 
sound  can  be  excluded.  An  absolutely  noise- 
less room  opens  up  numerous  new  possibili- 
ties of  research,  especially  in  the  fields  of 
sound  physiology  and  psychology.  For  this 
reason  rooms  have  been  constructed  in  many 
laboratories,  but  all  the  attempts  to  produce  a 
noiseless  room  that  are  known  to  the  writer 
are  more  or  less  unsuccessful,  with  the  excep- 
tion of  the  room  to  be  described  here. 

The  room  to  which  reference  is  made  is  in 
the  Physiological  Institute  of  the  University 
of  Utrecht,  Holland.  It  has  been  constructed 
under  the  direction  and  has  been  used  by 
Professor  H.  Zwaardemaker,  to  whom  I  am  in- 
debted for  permission  to  publish  the  present 
description.^ 

The  room  is  located  on  the  top  story  of  the 
laboratory  building  devoted  to  physiology. 
This  floor  of  the  building  is  little  used,  except 
for  the  sound  room,  and  tl^re  are,  conse- 
quently, few  footsteps  and  other  noises  in  the 
immediate  neighborhood  of  the  room.  The 
location  of  the  room  at  a  distance  from  the 

'  At  the  International  Physiological  Congress, 
Heidelberg,  August,  1907,  Professor  Zwaarde- 
maker read  a  description  of  the  room  and  showed 
lantern  slides  of  the  plans  of  construction.  Later, 
the  writer  had  an  opportunity  of  examining  the 
room  in  the  laboratory  at  Utrecht.  A  full  de- 
scription of  the  construction  is  to  be  published  in 
the  ZritHchrift  f.  Ohrmhcilhunde.  The  proof  of 
thin  article  was  in  the  writer's  hands  at  the  timo 
of  writing  the  present  account. 


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street  prevents  to  some  extent  the  transmission 
of  vibrations  and  jars  of  the  street  traffic. 
Moreover,  the  room  is  an  inside  one,  sepa- 
rated from  the  building  walls  by  other  rooms 
or  a  corridor,  although  in  its  construction,  as 
will  be  noted  below,  provision  is  made  for 
thorough  ventilation  and  the  entrance  of  sun- 
light. The  other  rooms  of  the  laboratory  on 
the  same  floor  are  comparatively  little  used. 


••••    •     . 

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and  by  surrounding  the  sound  room  they  help 
to  isolate  it. 

A  vertical  section  of  the  room  from  north  to 
south  is  given  in  the  accompanying  figure.  It 
will  be  seen  that  in  the  construction  a  small 
room  has  been  formed  to  the  south  of  the 
sound  room.  The  ceiling  of  the  small  room 
is  the  roof  of  the  building.  The  roof  has 
been  cut  to  form  a  window  which  admits  light 
and  air.  The  small  room  has  been  con- 
structed with  walls  nearly  as  sound-proof  as 
the  larger  room,  and  for  some  work  may  be 
used  as  an  additional  place  for  sound  experi- 
ments. When  closed,  it  also  serves  to  act  as 
a  dead  air  space  between  the  larger  room  and 
the  building  wall  and  roof. 


The  inside  measurements  of  the  sound  room 
are  as  follows:  Length,  228  cm.;  width,  220 
cm. ;  height,  228  cm. 

The  sides  of  the  room  are  built  of  six  layers. 
From  the  inside  outwards  the  layers  are  as 
follow:  (1)  Trichopiese,  about  5  cm.  thick. 
This  is  a  felt-like  material  made  of  horse  hair, 
and  from  exi)eriments  it  has  been  found  to 
have  very  low  coefficients  of  conduction  and 
reflection  of  sound.  This  layer  is  covered  with 
a  net  on  the  inner  side  (to  keep  the  hair  from 
falling)  and  then  fastened  with  nails  to  the 
second  layer,  which  is  more  stable.  (2)  Porous 
stone,  7.5  cm.  thick.  This  part  of  the  wall 
does  not  rest  directly  on  the  floor,  but  is  iso- 
lated from  the  floor  by  a  layer  of  sheet  lead, 
3  mm.  thick.  Next  there  is  (3)  a  dead  air 
space  from  2  to  3  cm.  thick.  Layer  4  is  a 
wood  partition,  2.5  cm.  thick.  The  outer- 
most layer  (6)  is  a  special  composition  of 
ground  cork,  Korkstein,  6  cm.  thick.  The 
outer  surface  of  the  last  layer  is  plastered, 
probably  mainly  for  appearance.  The  space 
between  layers  4  and  6  is  filled  with  a  mixture 


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of  ground  cork  and  sand.  The  thickness  of 
this  mixture  is  4  cm.  The  total  thickness  of 
the  walls  is,  therefore,  ahout  11  inches. 

The  ceiling  is  more  simply  made,  but  it  has 
an  analogous  "double-wall"  construction. 
From  within  outwards  there  is  (1)  Trichopiese, 
(2)  wood  ceiling,  to  which  the  Trichopiese  is 
fastened  and  which  in  turn  rests  on  the  porous 
stone  of  the  inside  layer  of  the  walls,  (3) 
sheet  lead,  3  mm.  thick,  (4)  an  air  space,  (5) 
a  second  wood  ceiling,  which  is  covered  with 
(6)  asphalt  paper,  (7)  sea  grass  and  (8) 
KorJcstein. 

The  floor  is  the  least  satisfactory  part  of  the 
construction.  The  floor  of  the  old  room  had 
to  be  used.  To  prevent  vibrations  passing 
from  board  to  board  the  joints  were  sawed 
through  and  the  crevices  thus  made  were  filled 
with  lead.  The  whole  floor  was  then  covered 
with  a  layer  of  lead,  3  mm.  thick,  and  over 
this  a  very  thick  (1  cm.)  carpet  has  been 
placed.  At  times  a  second  carpet  is  also  used. 
Had  the  original  floor  been  of  marble  or 
cement  it  is  probable  that  the  two  layers  (lead 
and  carpet)  would  have  been  as  satisfactory 
as  the  six  layers  of  the  walls. 

The  door  is  double.  The  outer  part  opens 
on  the  corridor.  It  is  an  ordinary  door,  made 
of  wood,  but  accurately  fitted  with  felt.  The 
inner  door  is  composed  of  three  layers.  The 
middle  layer  is  wood,  the  inner  or  room  layer 
is  Trichopiese,  and  the  outer  layer  is  Kork- 
stein.  This  inner  door  opens  into  the  room. 
There  is  the  usual  air  space  between  the  two 
doors.  The  door  is  part  of  one  of  the  long 
sides  of  the  room. 

Nearly  opposite  the  door  is  a  small  rect- 
angular window,  38  by  45  cm.  This  opens  into 
the  small  adjoining  room  to  the  south  and  is 
directly  opposite  the  window  in  the  roof. 
The  roof  window  opens  to  admit  light  and  air, 
but  the  opening  is  covered  with  a  fine  gauze 
screen  to  exclude  insects  and  especially  moths. 


WLen  both  windows  are  open  the  sun  can  get 
into  all  comers  of  the  room  and  the  room  may 
be  partially  ventilated.  With  doors  and 
windows  open  the  room  is  thoroughly  venti- 
lated. 

The  sound  stimuli  may  have  their  origin  in 
or  outside  the  sound  room.  If  the  source  of 
the  sound  is  in  an  adjoining  room  the  appa- 
ratus is  placed  in  a  cabinet,  isolated  from  the 
floor  by  a  lead  plate  and  felt,  and  covered  with 
the  same  materials.  This  isolation  still 
further  decreases  the  chance  of  these  noises  or 
tones  entering  the  room  through  floor,  ceiling 
or  walls  except  in  the  manner  that  is  desired. 

For  experiments  in  which  it  is  necessary  to 
have  the  origin  of  the  sound  stimuli  at  a  dis- 
tance from  the  subject  means  are  needed  for 
conducting  the  sound  into  the  room.  For  this 
reason  a  hole  was  bored  through  one  of  the 
walls  and  a  copper  tube  inserted.  This  tube 
is  fastened  to  a  marble  plate,  which  in  turn  is 
fastened  to  the  second  layer,  porous  stone,  of 
the  inner  wall.  The  wood  partition  is  here 
omitted  and  a  plate  of  load,  2.5  cm.  thick,  is 
used  for  the  outer  part  of  the  wall.  To  close 
the  copper  tube  lead  plugs  were  made,  one  of 
which  is  solid,  a  second  has  a  single  opening, 
1.5  cm.  diameter,  and  the  third  has  two  open- 
ings, each  0.8  cm.  diameter.  The  solid  lead 
plug  serves  to  keep  the  room  sound-proof  if  it 
is  not  necessary  to  conduct  the  sound  from 
without;  the  second  and  third  give  opportunity 
of  introducing  one  or  two  sound  stimuli,  re- 
spectively. 

The  room  is  fitted  with  electric  light  and 
wires  for  telephone  and  other  electrical  pur- 
poses. 

The  location  of  the  window,  on  the  south- 
em  side  of  the  room,  makes  it  jjossible  to 
have  the  room  lighted  by  the  sun  and  a  thor- 
ough ventilation  may  be  secured  in  tlu^  in- 
tervals of  a  series  of  experimentH.  Ono 
thing  has  not  been  solved  in  the  construction, 


viz.,  the  ventilation  of  the  room  during  a 
series  of  tests.  The  room  is  large  enough  to 
hold  one  person  for,  say,  a  half  hour  without 
discomfort  from  lack  of  oxygen,  and  the  use 
of  porous  material  in  the  construction  may 
make  it  possible  to  remain  a  longer  time  with- 
out ill  effect.*  For  a  series  of  tests  on  tones 
a  half  hour  is  sufficient  time  if  we  do  not  have 
to  deal  with  a  condition  of  the  ear  analogous 
to  the  adaptation  of  the  eye.  If  time  is  needed 
for  the  "  adaptation  "  of  the  ear  perhaps  some 
further  scheme  of  ventilation  may  be  required. 
On  this  point,  the  adaptation  of  the  ear,  we 
have  no  information  and  one  of  the  possibili- 
ties of  the  room  is  the  discovery  of  such 
adaptation. 

When  in  the  room,  some,  not  all,  persons 
experience  peculiar  sensations  from  the  ear 
(drum?),  corresponding  to  the  sensations  in 
slightly  compressed  air.  There  is  a  distinct 
feeling  of  pressure  which  is  subjective  and 
which  disappears  so  soon  as  a  sound  is  made, 
or  sound  stimuli  are  given. 

The  noiselessness  of  the  room  is  shown  by 
the  fact  that  one  hears  a  subjective  buzzing, 
similar  to  but  of  less  intensity  than  the  buzz- 
ing produced  by  large  doses  of  quinine. 
Many  normal  people  can  also  hear  their  own 
heart  sounds.  It  is  true  that  their  own  heart 
sounds  can  be  heard  by  some  in  rooms  not 
noiseless,  but  this  is  not  the  case  with  many 
normal  individuals  except  after  very  violent 
exercise.  In  the  room  a  few  swings  of  the 
leg  or  arm  is  often  sufficient  to  make  the  heart 
sounds  quite  distinct.  Other  body  noises  may 
also  be  heard.  If  a  movement  of  a  few  inches 
in  extent  is  made,  such  as  lightly  brushing  the 
foot  over  the  carpet  or  a  free  movement  of  the 
arm,  the  sound  is  distinctly  audible.  So  au- 
dible are  these  noises  that  one  must  be 
careful   not   to   move   when   experiments    are 

^On  this  point  I  failed  to  make  inquiries. 


in  progress.  A  further  proof  of  the  noise- 
lessness  of  the  room  is  to  be  found  in  the  fact 
that  a  shell  held  to  the  ear  does  not  appear 
to  give  forth  any  sound.  The  tones  for  which 
the  shell  is  resonant  are  absent.  It  should 
be  mentioned  again  here  that  the  felt-like  lin- 
ing of  the  room  eflFectually  stops  all  sound 
reflection.  Whatever  sounds  are  produced  or 
brought  into  the  room  are  in  this  respect 
simple;  they  cease  when  the  vibration  reaches 
the  wall. 

To  keep  the  room  fresh  and  clean,  in  addi- 
tion to  the  entrance  of  sunlight  and  fresh  air, 
dust  and  other  dirt  are  removed  by  a  me- 
chanical cleaner — the  so-called  compressed  air 
cleaner — and  it  is  disinfected  by  formalin 
vapor. 

In  experiments  during  the  past  three  or 
four  years  the  room  has  been  used  in  its  vari- 
ous conditions  of  evolution  and  in  its  final 
form  has  proved  to  be  most  satisfactory.  For 
many  years  it  will  doubtless  be  a  standard  for 
the  construction  of  similar  rooms  in  other  in- 
stitutions. Shepherd  Ivory  Franz 

Geobge  Washington  University 

govebnment  hospital  fob  the  insane 


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